Doppler echocardiographic evaluation of Hancock and Björk-Shiley prosthetic values

Gradient changes in bioprosthetic valve thrombosis: duration of anticoagulation and strategies to improve detection

Objective

Bioprosthetic valve thrombosis (BPVT) is increasingly recognised as a major cause of prosthetic dysfunction in the first years postimplantation. How early abnormal gradients can be detected prior to diagnosis and how fast they normalise with anticoagulant therapy is unknown. We set forth to (1) evaluate patterns of increase in gradients prior to BPVT diagnosis and (2) characterise time-course of response to anticoagulation.

Methods

Patients treated with warfarin for BPVT (1999–2019) with clinically significant reduction of mean gradients (≥25%) were identified retrospectively. Recovery was defined as gradient decrease ≥50%, to postimplantation or to normal-range gradients per position, model and size. Time-to-BPVT (implantation—BPVT diagnosis), potential diagnostic delay (first abnormal gradient by position, model and size—BPVT diagnosis) and time-to-recovery (BPVT diagnosis—complete resolution) were recorded.

Results

77 patients were identified; 32 (42%) aortic (23 surgical—12 porcine, 11 pericardial; 9 transcatheter); 24 (31%) mitral; 21 (27%) tricuspid. Median time-to-BPVT was 24, 21 and 10 months, respectively. Potential diagnostic delay was median 21 months for aortic, 4 months for mitral, but 0 for tricuspid. Recovery was significantly faster in mitral than aortic (median 2.5 vs 4.8 months, p=0.038) and tricuspid (median 5.9 months, p=0.025) positions. Porcine aortic valves responded faster than pericardial aortic valves (median 2.9 vs 20.3 months, p=0.004).

Conclusion

Gradients start to increase months before the clinical BPVT diagnosis. Recovery is faster in mitral and surgical aortic porcine valves; a longer warfarin trial seems indicated in tricuspid and surgical aortic pericardial valves.

Diagnostic evaluation of left-sided prosthetic heart valve dysfunction

Prosthetic heart valve (PHV) dysfunction is a rare, but potentially life-threatening, complication. In clinical practice, PHV dysfunction poses a diagnostic dilemma. Echocardiography and fluoroscopy are the imaging techniques of choice and are routinely used in daily practice. However, these techniques sometimes fail to determine the specific cause of PHV dysfunction, which is crucial to the selection of the appropriate treatment strategy. Multidetector-row CT (MDCT) can be of additional value in diagnosing the specific cause of PHV dysfunction and provides valuable complimentary information for surgical planning in case of reoperation. Cardiac magnetic resonance imaging (CMR) has limited value in the evaluation of biological PHV dysfunction. In this Review, we discuss the use of established imaging modalities for the detection of left-sided mechanical and biological PHV dysfunction and discuss the complementary role of MDCT in this context.

Doppler-catheter discrepancies in patients with bileaflet mechanical prostheses or bioprostheses in the aortic valve position

The aims of the present study were to investigate in vivo Doppler-catheter discrepancies in aortic bileaflet mechanical and stented biologic valves and evaluate whether these can be predicted using Doppler echocardiography. Results of in vitro studies of bileaflet mechanical valves suggested overestimation using Doppler gradients. Findings in stented biologic valves were conflicting. Patients who underwent valve replacement with a St. Jude Medical mechanical (n = 14, size 19 to 29) or a St. Jude Medical Biocor (Biocor, n = 13, size 21 to 25) valve were included. Simultaneous continuous Doppler recordings (transesophageal transducer) and left ventricular and aortic pressure measurements were performed using high-fidelity catheters. Gradients after pressure recovery were predicted from Doppler using a validated equation. Doppler overestimated catheter gradients in both the mechanical and Biocor. Mean Doppler catheter differences for the mechanical/Biocor were for mean gradients of 4 +/- 3 (SD; p = 0.002)/6 +/- 4 mm Hg (p = 0.002). There was a strong relation between catheter and Doppler gradients (r = 0.85 to 0.92). Doppler catheter discrepancy as a percentage of the Doppler mean gradient for the mechanical was median 41% (range -30% to 76%) and for the Biocor was median 35% (range -7% to 75%). The catheter-Doppler discrepancy was not significant using the predicted net gradient from Doppler. In conclusion, this was the first in vivo investigation of prosthetic valves using simultaneous Doppler and high-fidelity catheters. Doppler overestimated catheter gradients in both mechanical and stented biologic valves. However, the discrepancy can be predicted considering pressure recovery in the aorta.

Prosthetic heart valves: Types and echocardiographic evaluation

In the last five decades multiple different models of prosthetic valves have been developed. The purpose of this article is to provide a comprehensive source of information for the types and the echocardiographic evaluation of the prosthetic heart valves.

Hemolysis in Mechanical Bileaflet Prostheses: Experience With the Bicarbon Valve

BACKGROUND

Normal functioning mechanical heart valve prostheses are designed to have a certain degree of intrinsic structural regurgitation as a washout mechanism to avoid prosthetic thrombosis. However, intrinsic regurgitation leads to blood cell trauma and hemolysis. Information on hemolysis associated with mechanical bileaflet prostheses is scarce. This study evaluated factors influencing hemolysis in 197 Bicarbon mechanical bileaflet prostheses implanted in 164 patients.

METHODS

Serial office interviews, laboratory studies, and echocardiography evaluations were done in the surviving patients. An assay for measuring lactate dehydrogenase activity was developed, and the presence and severity of subclinical hemolysis was determined using reported criteria and analyzed at 1 and 2 years.

RESULTS

Hospital mortality was 5.5%. Follow-up was 98.1% complete. No patient had clinically significant or severe subclinical hemolysis. Serum lactate dehydrogenase levels were significantly higher when a paravalvular leak was documented (282 +/- 85 U/L versus 242 +/- 64 U/L; p = 0.0026). Subclinical hemolysis was significantly more frequent after mitral valve (p = 0.001) and double valve replacement (p = 0.001) than after aortic valve replacement, and was unrelated to prosthetic size or to geometric area index, even in those cases with effective orifice area index equal to or less than 0.85 cm2/m2 (p = 0.298).

CONCLUSIONS

Mild subclinical hemolysis is frequently associated with normal functioning Bicarbon heart valves. Subclinical hemolysis was significantly influenced by valve position but not by valve size or effective orifice area index and remained stable through time. The magnitude of hemolysis in Bicarbon prostheses compared favorably with that reported for other bileaflet heart valve prostheses.

Net pressure gradients in aortic prosthetic valves can be estimated by Doppler

BACKGROUND

In aortic prosthetic valves, both the Doppler-estimated gradients and orifice areas are misleading in the assessment of hemodynamic performance. The parameter of major interest is the net pressure gradient after pressure recovery (PR). We, therefore, investigated, in vitro, our ability to predict the net pressure gradient and applied the formulas in a representative patient population with 2 different valve designs.

METHODS

We studied the St Jude Medical (SJM) standard valve (size 19-27) and SJM Biocor (size 21-27) in an in vitro steady-flow model with simultaneous Doppler-estimated pressure and catheter pressure measurements. Using echocardiography, we also studied patients who received the SJM (n = 66) and SJM Biocor (n = 45).

RESULTS

In the SJM, we observed PR both within the prosthesis and aorta, whereas in the SJM Biocor, PR was only present in the aorta. We estimated the PR within the valve and within the aorta separately from echocardiographic in vitro data, combining a regression equation (valve) with an equation on the basis of fluid mechanics theory (aorta). The difference between estimated and catheter-obtained net gradients (mean +/- SD) was 0.6 +/- 1.6 mm Hg in the SJM and -0.2 +/- 1.9 mm Hg in the SJM Biocor. When these equations were applied in vivo, we found that PR had an overall value of 57 +/- 7% of the peak Doppler gradient in the SJM and 33 +/- 9% in the SJM Biocor.

CONCLUSIONS

The in vitro results indicate that it is possible to predict the net pressure gradient by Doppler in bileaflet and stented biologic valves. Our data indicate that important PR is also present in stented biologic valves.

Doppler hemodynamics of 51 clinically and echocardiographically normal pulmonary valve prostheses

OBJECTIVE

To determine the normal Doppler hemodynamics of various pulmonary valve prostheses (PVPs).

PATIENTS AND METHODS

We retrospectively analyzed comprehensive Doppler echocardiographic examinations of 51 patients (mean age, 27.8 years; range, 1-59 years) with PVPs that were normal on clinical and 2-dimensional echocardiographic examinations to establish the normal hemodynamics of various types and sizes of PVPs. The earliest complete postoperative transthoracic echocardiogram was identified for each patient. Doppler examinations were analyzed for peak instantaneous velocity, right ventricular outflow tract velocity, and peak and mean systolic gradient. The frequency of prosthetic regurgitation was also noted.

RESULTS

The average +/- SD peak instantaneous velocity for all PVPs was 2.24+/-0.6 m/s, with an average peak systolic gradient of 20.4+/-10.4 mm Hg and an average mean systolic gradient of 11.0+/-5.1 mm Hg. The mean right ventricular outflow tract velocity was 1.0+/-0.2 m/s. Pulmonary homografts were found to have significantly lower peak velocities (average, 1.8+/-0.6 m/s) than all heterografts combined (average, 2.4+/-0.5 m/s; P=.002). Prosthetic regurgitation was more common in pulmonary homografts (88%) than in heterografts combined (29%; P<.001).

CONCLUSION

This study establishes the normal range for Doppler hemodynamics of various PVPs, specifically homografts and heterografts, in both pediatric and adult patients.

Stentless bioprostheses have ideal haemodynamics, even in the small aortic root

OBJECTIVE

To determine normal Doppler and 2D gradients and flow characteristics of the Freestyle stentless aortic bioprosthesis related to valve size.

BACKGROUND

The Freestyle stentless aortic bioprosthesis is one of the newer aortic xenografts. Only limited data are available of the echocardiographic flow characteristics during a mid-term follow-up period of this valve. Therefore valve performance related to valve size was measured during a follow-up period of two years.

METHODS

175 consecutive patients with a Freestyle aortic bioprosthesis underwent an echocardiographic and Doppler examination according to a common protocol. Investigations were done within 4 weeks after operation, after 3 to 6 months, and after 1 and 2 years.

RESULTS

With a valve size from 19 to 27 mm mean gradients decreased from 8.0 +/- 5.1 mmHg at discharge to 5.8 +/- 3.8 mmHg after 3-6 months (p < 0.001). Thereafter gradients remained stable. The performance index, the ratio of the measured effective orifice area in the patient divided by the effective orifice area measured in vitro increased from 69 +/- 20% at discharge to 79 +/- 29% after one, two and three years. Performance index was especially very high in the smaller sized valves with a performance index of 85 +/- 17% for the 21 mm valve. During follow-up mean gradients remained below 10 mmHg even in the 21 mm valve.

CONCLUSION

Stentless xenografts have ideal haemodynamics, even in the small aortic root.

Postoperative exercise tolerance after aortic valve replacement by small-size prosthesis: functional consequence of small-size aortic prosthesis

OBJECTIVES

The objective of this study was to determine whether a small-size valve prosthesis contributes to exercise intolerance, as assessed by VO2 measurement during an exhaustive cycle ergometer exercise.

BACKGROUND

The determinants of exercise capacity after mechanical aortic replacement are not well known. The selection of small valve sizes has, however, been described as an independent predictor of exercise intolerance as assessed by exercise duration. Maximal oxygen uptake (VO2max) is a good index of exercise tolerance.

METHODS

Fourteen patients were eligible, with a mean age of 62 +/- 6 years. Before surgery, the mean left ventricular ejection fraction (LVEF) was 73 +/- 8%. Two valve types with small diameter (19 to 21 mm) were used: Medtronic Hall and St Jude Medical. A healthy sedentary control group (n = 14) paired for age, weight and size was constituted. After one year of follow-up, cardiorespiratory tests were performed. In addition, the gradients through the prostheses were determined by continuous pulse Doppler at rest and immediately after the cardiorespiratory test. RESULTS The exercise tolerance was not significantly different between the control group and patient group: VO2 peak (21.7 vs. 20.4 ml/kg/min; p = 0.42), workloads (115 vs. 93 W; p = 0.13) and ventilatory parameters were similar. The mean and peak gradients at rest and during exercise were not correlated with VO2max.

CONCLUSIONS

Valve replacement by small aortic prosthesis does not seem to be a factor of exercise intolerance as assessed by VO2max in patients without LVEF dysfunction before surgery.

Echocardiographic parameters of the freestyle stentless bioprosthesis in aortic position: the European experience

The objective of this study was to determine normal Doppler and 2-dimensional characteristics of the Freestyle stentless aortic bioprosthesis. The Freestyle aortic bioprosthesis is a new type of aortic xenograft, and experience is limited. We therefore determined the normal range of echocardiographic and Doppler examinations of this valve. Three hundred thirty-nine consecutive patients with a Freestyle aortic bioprosthesis underwent an echocardiographic and Doppler examination according to a common protocol. Investigations were done within 4 weeks after operation, after 3 to 6 months, and after 1, 2, and 3 years. With a valve size from 19 to 27 mm, mean gradients decreased from 7.9 +/- 5.1 mm Hg at discharge to 5.5 +/- 3. 8 mm Hg after 3 to 6 months (P <.001). Thereafter, gradients remained stable. Effective orifice area 1 year after implantation was 1.59 +/- 0.58 cm(2) for the 21-mm valves, 1.92 +/- 0.74 cm(2) for the 23-mm valves, 2.03 +/- 0.64 cm(2) for the 25-mm valves, and 2.52 +/- 0.72 cm(2) for the 27-mm valves (P <.001). The performance index, the ratio of the measured effective orifice area in the patient divided by the effective orifice area measured in vitro, increased from 67% +/- 20% at discharge to 82% +/- 29% after 1, 2, and 3 years. Performance index was especially very high in the smaller-sized valves. After implantation with the subcoronary technique or root-inclusion technique, small cavities could be seen between the native aortic root and the Freestyle valve. Doppler values were evaluated for the Freestyle stentless porcine bioprostheses in the aortic root. Gradients appear to be close to those measured in native valves over a time period of 3 years.

Simultaneous Doppler and catheter transvalvular pressure gradients across St Jude bileaflet mitral valve prosthesis: in vivo study in a chronic animal model with pediatric valve sizes

A mixture of valve types has been used in previous in vivo studies to assess the accuracy of Doppler echocardiography compared with catheter-measured pressure gradients across prosthetic mitral valves. However, limited data exist regarding the most commonly used bileaflet mechanical valve. We studied 14 sheep with St Jude Medical mechanical mitral valves. Continuous wave Doppler data were obtained across each of the 3 valve orifices. Hemodynamic data were obtained simultaneously by direct measurements with catheters. Valve sizes commonly used in the pediatric population in the mitral position (23 mm, 25 mm, and 27 mm) were studied. Linear regression analyses of Doppler-predicted versus catheter-measured gradients provided correlation coefficients ranging from 0.75 to 0.91. Agreement analysis demonstrated a scatter of Doppler data about the regression line. Although a reasonably good correlation of Doppler-predicted peak and mean pressure gradients across bileaflet mechanical valves exists in the mitral position, caution is needed when this method is applied to patients. Doppler overestimation was greatest across the 23-mm valves. Analyses of the specific orifice interrogated demonstrated higher estimated pressure gradients across the central orifice compared with the side orifices.

Application of proximal isovelocity surface area method to determine prosthetic mitral valve area

BACKGROUND

In this study, we investigated the accuracy of orifice area determination of the prosthetic valve (Biocor) by using proximal isovelocity surface area method (PISA). Thirty-two patients (26 women, 6 men; mean age 44 +/- 8.1 years) were studied. Eleven patients were in normal sinus rhythm and the rest were in atrial fibrillation. Associated valvular lesions were mild aortic regurgitation in 12 patients and moderate tricuspid regurgitation in 19 patients. Sizes of prosthetic valves were 27 to 31, and implantation duration was 4 to 8 years.

METHODS AND RESULTS

We analyzed the flow convergence zone proximal to the valve orifice with the concept of a hemispheric model. Mitral valve area (MVA) calculation was formulated by MVA = 2pi r2 x Va/Vm x (Vm/Vm-Va), where Vm is the maximal mitral velocity and Vm/Vm - Va is a correction factor to account for flattening of isotachs near the prosthetic orifice. MVA calculations by PISA were compared with pressure half-time (PHT), continuity equation (CONT), and color flow area (CFA) methods. Mitral valve areas were 2.17 +/- 0.17 cm2, 2.22 +/- 0.21 cm2, 2.19 +/- 0.22 cm2, and 2.16 +/- 0.17 cm2 in PISA, CFA, PHT, and CONT methods, respectively. Values in the comparison of MVA measurements by different methods were PISA vs PHT, r =.86; PISA vs CFA, r =.77; and PISA vs CONT, r =.89.

CONCLUSIONS

The PISA method gives reliable estimates of large orifices such as prosthetic valves. Although the best correlation was seen with the CONT method, results of this study also confirmed that the PISA method can be applied with reasonable accuracy.

Dobutamine Stress Test to Evaluate Different Sizes of Prosthetic Aortic Valves

Dobutamine stress testing and Doppler echocardiography were used to assess hemodynamics in 27 patients aged 16 to 54 years with various sizes and types of aortic valve prosthesis. All patients underwent a symptom-limited treadmill exercise test within two days of the dobutamine test. There was no significant difference in ejection fractions and transvalvular gradients at rest and during dobutamine stress between St. Jude Medical, Medtronic-Hall, and Carbomedics valves. Exercise duration did not differ significantly among the different types of valve. When patients were classified by their underlying lesion, those with aortic stenosis and those with aortic insufficiency had similar ejection fractions and transvalvular gradients at rest and during dobutamine stress. The mean and peak transvalvular gradients at rest and during dobutamine stress were significantly different in patients with different valve sizes but the extent of the increase in gradients during stress was not significant. Linear regression analysis revealed that both peak and mean gradients during dobutamine stress could be predicted by the resting gradients. There was a negative correlation between valve size and gradients at rest and during stress, while there was a significant correlation between exercise duration and valve size. Dobutamine stress echocardiography was useful for studying hemodynamics in patients with aortic valve prostheses and the findings show that valvular size was the main determinant of exercise capacity.

Clinical, echocardiographic, and pathologic features of aortic wall dehiscence of porcine bioprosthetic valves: a cause of rapidly progressive mitral regurgitation and heart failure after bioprosthetic mitral valve replacement

The aim of this study was to define the clinical, echocardiographic, and pathologic correlates of commissural dehiscence of aortic wall from the stent post of the porcine bioprostheses in the mitral position. This form of valve degeneration was found in 5 of 23 explanted mitral bioprostheses. A thickened, separated aortic wall at multiple commissural sites along with other evidence of valve degeneration was identified in the three patients who had chronic congestive heart failure. A large dehiscence at a single commissural site with otherwise normal valve morphology was present in the two patients who had acute heart failure. Two dimensional/Doppler echocardiography showed a prolapsing or a flail anteriorly positioned leaflet and an eccentric posteriorly directed mitral regurgitation jet in all patients. These echocardiographic findings in patients with a porcine bioprosthetic mitral valve should suggest commissural dehiscence from the aortic wall as a possible mechanism of valve failure. Exclusive involvement of the porcine aortic bioprosthesis placed in the mitral position along with involvement of strut of the bioprosthesis facing the aortic root in all cases suggests excessive hemodynamic stress on the valve in the mitral position and in particular on the anteriorly placed strut as the potential cause of this form of valve degeneration.

Summary of the Mayo Clinic experience with direct left ventricular puncture

Hemodynamic assessment of patients with prosthetic valves can be challenging. Noninvasive techniques may be limited by interference from the prosthetic material, whereas access to the left ventricle for direct pressure measurements often is not possible using common methods. The technique of direct, percutaneous left ventricular puncture has been proven to be a safe method that often provides needed data to help manage difficult clinical situations. We report our 8-yr experience with this technique for assessment of patients with valvular prostheses. Direct left ventricular puncture is a safe technique in patients with prior cardiac surgery and provided significant diagnostic information in the set of patients with multiple valvular prostheses.

Hemodynamic Comparison by Doppler Echocardiography of Valves in the Aortic Position: Value of the Continuity Equation to Assess Prosthetic Dysfunction

In 281 patients, we used Doppler echocardiography to compare the hemodynamic performance of different aortic prosthetic valves at three postoperative stages and investigated the value of the continuity equation in diagnosing aortic prosthetic obstruction. A baseline study was performed in 163 patients, a 5 +/- 2-month follow-up study was performed in 103 patients, and a 15 +/- 5-month follow-up study was performed in 65 patients. From baseline to the second study, left ventricular diastolic diameter, heart rate, and maximum (MG) and mean Doppler-derived gradient (MeG) decreased significantly, and left ventricular shortening fraction, systolic blood pressure, stroke volume, and prosthetic valvular area (PVA) increased significantly. No changes were found between the second and third studies. Thus, noninvasive hemodynamic values at the time of follow-up are reported in 171 patients: 86 with Björk-Shiley Monostrut, 27 with Carbomedics, 11 with Medtronic-Hall, 18 with Hancock modified, and 29 with Toronto valve bioprosthesis. Patients implanted with the Toronto had a larger prosthetic size (Monostrut 23 +/- 2 mm, Carbomedics 23 +/- 3 mm, Medtronic-Hall 23 +/- 2 mm, Hancock 23 +/- 2 mm, Toronto 25 +/- 2 mm, P < 0.01) despite a similar body surface area. MeG and MG were lower (MeG [in mmHg] Monostrut 12 +/- 5, Carbomedics 14 +/- 6, Medtronic-Hall 19 +/- 6, Hancock 11 +/- 4, Toronto 7 +/- 5; P < 0.01 between Toronto and all others), and PVA was greater (Monostrut 2.0 +/- 0.7 cm(2), Carbomedics 1.8 +/- 0.8 cm(2), Medtronic-Hall 1.6 +/- 0.7 cm(2), Hancock 1.7 +/- 0.5 cm(2), Toronto 2.2 +/- 0.9 cm(2); P < 0.01 between Toronto and Carbomedics, Medtronic-Hall, and Hancock), even compared with the same sizes in the other valves. A PVA of 0.9 cm(2) or less and MeG of 28 mmHg or more identified prosthetic obstruction with 100% sensitivity and 99% specificity. Hemodynamics change significantly from the early to the late postoperative state. The Toronto valve stentless porcine bioprostheses performs hemodynamically better than other valves. PVA measurement using the continuity equation may accurately identify prosthetic obstruction.

Normal echocardiographic characteristics of the Sorin Bicarbon bileaflet prosthetic heart valve in the mitral and aortic positions

Doppler echocardiographic characteristics of normally functioning Sorin Bicarbon prostheses were prospectively assessed in 226 consecutive patients (135 male and 91 female patients, mean age 61 +/- 10 years) with 233 valves in the mitral (n = 67) and aortic (n = 166) positions whose function was considered normal by clinical and echocardiographic evaluation. Patterns of "normal" transprosthetic leakage were assessed with transthoracic echocardiography in all valves and with transesophageal echocardiography in six selected mitral valve prostheses. For the mitral valve prostheses, we found that peak and mean gradient, as well as pressure half-time, were not significantly different in either the 25 or the 31 mm valves (median values from 15 to 10 mm Hg, from 4 to 4 mm Hg, and from 70 to 83 ms; p = Not significant for all). On transthoracic study, 12 patients (17%) with a Sorin Bicarbon valve in the mitral position showed minimal transprosthetic leakage. On transesophageal study, all patients showed a transprosthetic leakage whose spatial distribution had a complex pattern: in planes orthogonal to the leaflet axis, two to four jets arising from the hinge points and converging toward the center of the valve plane could be visualized; in planes parallel to the leaflet axis, there were three jets, the two lateral ones diverging and the central one perpendicular to the valve plane. For the aortic valve prostheses, there was a significant decrease in transprosthetic gradients and an increase in effective orifice areas as prosthesis size increased. Peak and mean gradients decreased from a median value of 25 and 13 mm Hg in the 19 mm valves to 9 and 5 mm Hg in the 29 mm valves, respectively. Effective prosthetic valve area calculated with the continuity equation increased from a median value of 0.97 cm2 for the 19 mm size valves to 3.45 cm2 for the 29 mm size. With analysis of variance, effective prosthetic aortic valve area differentiated various valve sizes (F = 40.9, p < 0.0001) better than peak (F = 10.3, p < 0.0001) or mean (F = 8.04, p < 0.0001) gradients alone did. Furthermore, effective prosthetic aortic valve area correlated better than peak and mean gradients with prosthetic size (r = 0.76, r = -0.45, and r = -0.39, respectively). On transthoracic study, 109 patients (66%) showed minimal transprosthetic leakage. These normal values, obtained in a large number of patients with normofunctioning mitral and aortic Sorin Bicarbon valves, may help to identify Sorin Bicarbon prosthesis dysfunction.

Extent and pattern of regression of left ventricular hypertrophy in patients with small size CarboMedics aortic valves

OBJECTIVE

To assess the extent and pattern of regression of left ventricular hypertrophy after valve replacement for aortic stenosis, we studied 26 patients receiving either 19 or 21 mm CarboMedics valves (group I, 13 patients) or either 23 or 25 mm CarboMedics valves (group II, 13 patients). The studies were done before the operation and after 3 years, and results were compared with those of 10 control patients.

METHODS

Left ventricular end-diastolic and end-systolic diameters and volumes, ejection fraction and fractional shortening, and interventricular septum and posterior wall thickness were measured. The ratio between interventricular septum and posterior wall thickness, the ratio between left ventricular wall thickness and left ventricular chamber radius, and the left ventricular mass were then calculated.

RESULTS

At follow-up there was a significant reduction in the left ventricular mass, interventricular septum, and posterior wall thickness for both patient groups (p < 0.01). However, only the posterior wall thickness reached normal values; the interventricular septum and the left ventricular mass indices were still significantly greater than in the control group (p < 0.01). Because of the incomplete regression of interventricular septal hypertrophy, the ratio between interventricular septum and posterior wall thickness was similar between both patient groups but it was significantly higher than in control subjects (p < 0.01). The ratio between wall thickness and chamber radius did not decrease significantly in group II patients, in whom it remained above the control values.

CONCLUSION

Having a bileaflet aortic prosthesis of one size larger did not seem to significantly influence the pattern and the extent of regression of left ventricular hypertrophy after an intermediate period of follow-up.

Early in vivo experience with the Hemodynamic Plus St. Jude Medical heart valves in patients with narrowed aortic annulus

BACKGROUND

Small aortic orifice primarily resulted in heart prosthesis mismatch in a significant number of patients. The Hemodynamic Plus (HP) series of St. Jude Medical heart valves represents an interesting innovation, allowing a larger valve orifice area with an equivalent tissue annulus diameter.

METHODS

Hemodynamic characteristics of the 21-mm HP St. Jude Medical valve were prospectively compared with those of the standard 21-mm and 23-mm St. Jude Medical valves in three groups of 22 patients. Patients were selected from a database to be rigorously matched for age, sex, body surface area, functional class, underlying lesion, native valve opening area, left ventricular function, and preoperative peak and mean valve gradients. Postoperative evaluation (follow-up ranging from 3 to 24 months; mean, 11.5 months) included clinical examination and echocardiographic studies.

RESULTS

There was no operative mortality or significant perioperative complications. Short-term clinical follow-up was marked by a complete absence of valve-related complications. Presently, all but 1 patient in the 21-mm HP group and 2 in the 21-mm standard group are in New York Heart Association functional class I. Doppler echocardiography-derived mean and maximal pressure gradients were significantly lower in the 21-mm HP group (8.1 +/- 1.9 and 16.4 +/- 3.4 mm Hg) than in the 21-mm standard group (13.4 +/- 3.9 and 21.2 +/- 4.3 mm Hg; p = 0.002 and p = 0.0004, respectively), confirming the better hemodynamic performance already described in in vitro studies. Pressure gradients did not differ significantly between the 21-mm HP and the 23-mm standard groups. The 21-mm HP valve demonstrated the highest performance index; 0.66 +/- 0.08, compared with 0.49 +/- 0.09 for the 21-mm standard valve (p < 0.001) and 0.59 +/- 0.07 for the 23-mm standard valve (p < 0.001).

CONCLUSIONS

In vivo hemodynamic performance of the 21-mm HP valve corresponds closely to that of the 23-mm standard valve and is substantially better than that of the 21-mm standard valve. The 21-mm HP St. Jude Medical valve demonstrates excellent hemodynamic characteristics and can be recommended in normal-sized adult patients with narrow aortic root. This valve will minimize the need for aortic annulus enlargement.

Comparison of hemodynamic performances of St. Jude Medical and CarboMedics 21 mm aortic prostheses by means of dobutamine stress echocardiography

Dobutamine stress Doppler echocardiography was used to compare the hemodynamic performance of two small aortic bileaflet prostheses. Nineteen patients (14 female, mean age 64 years) who had undergone aortic valve replacement with 21 mm bileaflet valve prostheses (St. Jude Medical valve, n = 9, or CarboMedics valve, n = 10) were studied. Dobutamine infusion was started at a rate of 5 micrograms.kg-1.min-1 and increased to 10 and 20 micrograms.kg-1.min-1 at 15-minute intervals. Under maximum stress, heart rate and cardiac output increased by 70% and 120%, respectively, and mean arterial blood pressure decreased by 9%. Pulsed-wave and continuous-wave Doppler studies were performed at rest and at the end of each stage. Velocity ratio, effective orifice area, performance index, and discharge coefficient of the valve were calculated, and peak and mean velocities and pressure drops across the prostheses were measured. Dobutamine infusion produced similar increases in cardiac output in all patients. Effective orifice areas, discharge coefficients, and performance indexes were comparable for the two valve groups both at rest and maximum stress. Transvalvular velocities and pressure drops were also similar in the two valve groups. Transvalvular pressure drops were also comparable in patients with large body surface area. Dobutamine stress echocardiography is useful in the evaluation of the hemodynamic performance of prosthetic heart valves. St. Jude Medical and CarboMedics 21 mm prostheses have equally favorable hemodynamic performances in most patients under conditions of high cardiac output.

Evaluation of St. Jude Medical mitral valve function by exercise Doppler echocardiography

The aim of this study was to detect borderline mitral valve dysfunction in 100 asymptomatic patients with a St. Jude Medical valve. We studied rest and exercise hemodynamics by Doppler echocardiography. Study patients were divided into two groups according to the time since surgery: group A had valves implanted less than 5 years ago (44 patients), group B had valves implanted more than 5 years ago (56 patients). Although patients had no clinical signs of valve dysfunction, group B was found to have significant reduction of mitral valve area (p < 0.05). In the group A patients, mean gradients at rest increased from 4 +/- 2, 4 +/- 2, and 3 +/- 1 mmHg in valve sizes of 25, 27, and 29 mm, respectively, to 7 +/- 2, 7 +/- 3, and 5 +/- 2 mmHg with exercise. In the group B patients, mean gradients at rest increased from 7 +/- 1, 6 +/- 2, and 5 +/- 1 mmHg to 14 +/- 3, 13 +/- 3, and 10 +/- 4 mmHg, respectively, after exercise. The percent increase (mean) in peak pressure gradient with exercise was significantly higher in group B (more than 100%) than in group A (less than 80%) (p < 0.01). The percent increase in mean gradient with exercise was also significantly higher in group B (more than 100%) than in group A (less than 75%). In conclusion, patients with reduced valve area and more than a 100% increase of peak and mean gradients should be followed up carefully. If any signs or symptoms of heart failure develop, they must be considered as candidates for surgery.

Improved Doppler assessment of the Bjork-Shiley mitral prosthesis using the continuity equation

To assess whether derivation of an effective mitral prosthetic valve area using the continuity equation provides an improved functional assessment of the Bjork-Shiley mitral prosthesis over the pressure half-time method, Doppler echocardiographic studies were performed in 43 patients 12 +/- 7 months following the valve replacement. Effective valve orifice area used as the standard for comparison was determined by a hydraulic formula validated in vitro over a wide range of flow rates. All patients were clinically stable, without evidence of prosthetic dysfunction or aortic regurgitation. Prosthetic mitral valve orifice area determined by the hydraulic formula, by the continuity equation and by pressure half-time method for all prostheses sizes averaged 1.6 +/- 0.46 cm2, 1.83 +/- 0.56 cm2 and 2.34 +/- 0.48 cm2, respectively. Effective valve orifice area by the hydraulic formula had a strong correlation with that derived by the continuity equation (r = 0.86; P < 0.0001; standard error of estimate (S.E.E.), 0.12 cm2), but an insignificant correlation with the area calculated by the pressure half-time method (r = 0.24). Prosthetic mitral valve areas determined by the continuity equation and by pressure half-time method also correlated poorly (r = 0.24). Pressure half-time was affected by heart rate, diastolic filling period, left ventricular fractional shortening and presence of atrial fibrillation (P < 0.001). Thus, using the standard continuity equation to determine the orifice area of the Bjork-Shiley prosthesis in the mitral position provides improved assessment compared with the pressure half-time method.

Southwestern Internal Medicine Conference: clinical applications of transesophageal echocardiography

Transesophageal echocardiography has emerged recently as a powerful cardiac imaging tool. The strengths and limitations of transesophageal echocardiography are reviewed. The clinical use of transesophageal echocardiography in aortic dissection, endocarditis, mitral valve disease, prosthetic heart valves, stroke, and miscellaneous other conditions is discussed.

Doppler hemodynamic profiles of 82 clinically and echocardiographically normal tricuspid valve prostheses

BACKGROUND

Normal Doppler hemodynamics for tricuspid prostheses have not been well characterized in a large group of patients. Therefore, we analyzed comprehensive Doppler echocardiographic examinations of 82 patients with tricuspid prostheses that were normal by clinical and two-dimensional echocardiographic examinations to establish the normal hemodynamics of various types and sizes of tricuspid prostheses.

METHODS AND RESULTS

The earliest complete postoperative echocardiographic study from each patient was chosen for analysis. Doppler examinations were analyzed on an off-line station from tapes or Doppler strip charts. Early velocity, atrial velocity, end-diastolic velocity, pressure half-time, and mean gradient were obtained by digitizing tricuspid velocity curves. The incidence of "physiological" tricuspid prosthetic regurgitation was noted. Ten Doppler cycles were measured for each patient, and maximal, minimal, and average measurements were recorded. The mean values +/- SD of early velocity, atrial velocity, end-diastolic velocity, mean gradient, and pressure half-time and incidence of mild prosthetic regurgitation were reported for each type of prosthesis, as were highest Doppler measurements for each valve type. Average pressure half-time was significantly lower for St Jude than for heterograft prostheses (P = .04). There were no significant differences between the valve types for mean gradient, early velocity, or incidence of prosthetic regurgitation. Increasing prosthesis size was associated with lower average pressure half-time for heterograft prostheses (P = .024). Average differences (respiratory- and cycle-length-dependent) between maximal and minimal values for 10 cardiac cycles were established for each prosthesis.

CONCLUSIONS

This study establishes normal ranges for Doppler hemodynamics of various tricuspid prostheses and emphasizes the importance of measuring multiple cycles for each tricuspid prosthesis, regardless of cardiac rhythm.

Effect of prosthetic valve malfunction on the Doppler-catheter gradient relation for bileaflet aortic valve prostheses

BACKGROUND

Considerable discrepancies between Doppler and catheter gradients caused by localized gradients and pressure recovery have been reported for normal bileaflet aortic valve prostheses.

METHODS AND RESULTS

To examine whether this Doppler-catheter gradient relation is affected by prosthetic valve malfunction, a 19-mm CarboMedics aortic valve was simultaneously studied with continuous-wave Doppler and catheter technique in normal function and in various states of malfunction ranging from slightly restricted opening to total occlusion of one leaflet. For each functional status, peak and mean gradients were measured at eight different flow rates (cardiac output, 2.0-6.0 L/min). Excellent correlation between Doppler and catheter gradients was found regardless of the valve function (r = 0.99, SEE = 1.0-3.3 mm Hg). However, the relation between Doppler and catheter gradient was highly dependent on the function of the valve as shown by a variation of slopes from 1.08 to 2.08. For the normally functioning valve (angle between flow axis and leaflet 5 degrees), peak and mean Doppler gradients were approximately twice the catheter gradients (slope, 2.08 and 2.03 for peak and mean gradients, respectively). Slightly restricted opening of one leaflet (22 degrees) significantly altered the Doppler-catheter gradient relation, and slopes decreased to 1.69 (p < 0.01) and 1.52 (p < 0.001) for peak and mean gradients, respectively. The differences between Doppler and catheter gradients significantly decreased with further restriction of valve opening, and slopes ranged from 1.25 to 1.41 for angles between 34 degrees and 52 degrees. When one leaflet was totally occluded, the slope finally dropped to 1.08 for both peak and mean gradients, and Doppler gradients were only slightly greater than catheter gradients. Gradients increased with malfunction of the valve caused by reduction of the effective orifice area. However, the increase of Doppler gradients was considerably smaller than the increase of simultaneous catheter gradients.

CONCLUSIONS

The discrepancies between Doppler and catheter gradients that have been reported for normally functioning bileaflet aortic valve prostheses may be reduced or even disappear in patients with malfunctioning valves. Furthermore, the increase of Doppler gradients caused by malfunction of the valve may underestimate the true hemodynamic changes.

Pitfalls in the echo-Doppler diagnosis of prosthetic valve disorders

Assessment of artificial heart valves is a classic example of pitfalls in Doppler and color flow echocardiography. These limitations should be analyzed in the context of the most common clinical conditions associated with prosthetic valve dysfunction, that is, assessment of stenosis, regurgitation, endocarditis, and source of emboli. Estimation of the mean transvalvular gradient in addition to valve areas may avoid potential problems of over- or underestimation of stenotic lesions. The combination of acoustic attenuation, acoustic shadowing, and jet(s) eccentricity makes accurate grading of prosthetic regurgitation difficult and often frustrating. Reverberations and side lobe are frequent artifacts that decrease the ability of two-dimensional echocardiography to identify endocarditis-induced lesions such as vegetations and abscesses, as well as potential sources of emboli such as thrombus and atrial septal abnormalities. Transesophageal echocardiography has provided a new window in the evaluation of prosthetic cardiac valve function. With this approach, high frequency, high resolution transducers greatly improve the quality of ultrasound and color flow Doppler images that result in a higher diagnostic yield. In patients with suspected mitral prosthesis malfunction, transesophageal echocardiography is the method of choice. Contrast study during the transesophageal examination increases the sensitivity to detect potential sources of emboli such as patent foramen ovale. The improvement in diagnostic accuracy may allow one to avoid further diagnostic tests and, in selected patients, it may facilitate optimal timing of a surgical intervention.

Comparison of transthoracic and transesophageal echocardiography for detection of abnormalities of prosthetic and bioprosthetic valves in the mitral and aortic positions

Two-dimensional echocardiography is the diagnostic procedure of choice for evaluation of prosthetic valve abnormalities. However, transthoracic echocardiography (TTE) may be limited owing to acoustic shadowing and poor acoustic windows. Some of these limitations may be overcome by transesophageal echocardiography (TEE). One hundred twenty-six patients with 148 prosthetic valves (113 bioprostheses and 35 mechanical devices) were studied by M-mode and 2-dimensional TTE and TEE. Prosthetic valve morphology was confirmed by surgery or autopsy in all cases; 124 prostheses were classified as diseased (33 endocarditis, 8 thrombi, and 83 degeneration defined as leaflet thickening > 3 mm with restricted motion) and 24 as normal. Prosthetic valve endocarditis and thrombi were correctly identified by TTE in 12 of 33 (36%) and 1 of 8 (13%) prostheses, respectively, but could be diagnosed by TEE in 27 of 33 (82%; p < 0.001) and 8 of 8 (100%; p < 0.01), respectively. Compared with TTE, TEE had a higher sensitivity for morphologic prosthetic valve abnormalities in patients with either bioprostheses (88 [87%] vs 66 [65%] of 101 prostheses; p < 0.01) or mechanical devices (19 [83%] vs 5 [22%] of 23 prostheses; p < 0.01) and in patients with a prosthesis in either the aortic (49 [77%] vs 32 [50%] of 64; p < 0.01) or mitral (58 [97%] vs 39 [65%] of 60; p < 0.001) position. Overall, sensitivity and specificity were 57 and 63%, respectively, for TTE, and 86 and 88%, respectively, for TEE.(ABSTRACT TRUNCATED AT 250 WORDS)

Doppler-derived pressure differences in normally functioning aortic valve prostheses. Studies in Björk-Shiley monostrut and Biocor porcine prostheses

To determine the normal range of maximum and mean Doppler-derived pressure differences for mechanical and bioprosthetic valves in the aortic position, Doppler echocardiography was performed on 239 stable patients with normally functioning Björk-Shiley monostrut (BSM, n = 185) or Biocor porcine (n = 54) prostheses. The interval from aortic valve replacement to echocardiography was 3-9 days. Maximum and mean pressure differences were significantly greater in 21 mm than in 25 or 27 mm BSM prostheses. The pressure differences in 23 mm BSM valves did not diverge significantly from those in 21, 25 or 27 mm valves. The mean pressure difference did not exceed 30 mm Hg in any type or size of studied prosthesis. No significant differences were found in pressure gradients in comparisons between BSM and Biocor prostheses of corresponding sizes. The calculated velocity ratio for BSM prostheses was not significantly influenced by the valve size. We suggest that the normal range of Doppler-derived maximum and mean pressure differences determined in this study be adopted as reference in evaluations of aortic BSM and Biocor valve prostheses.

Assessment of spatial and temporal velocity profiles distal of normally functioning Björk-Shiley prosthesis by the Doppler method

By Doppler echocardiography, the performance of heart valve prostheses is assessed with the aid of maximal transprosthetic velocities, which, however, may not be representative for the full spatial velocity profile in the vicinity of mechanical valve substitutes due to flow separation by the open occluder. The purpose of this study was to determine characteristics of velocity profiles downstream of a normally functioning Björk-Shiley prosthesis. In a pulsatile flow apparatus, different flow rates of 6.3 and 8.4 l/min were delivered. Using a spatially and temporally resolving ultrasonic Doppler method, velocity profiles 20 and 30 mm distal from the prosthesis were registered and displayed in a three-dimensional grid. The spatial velocity profile was found to deviate substantially from a flat profile at these transducer positions at the two flow conditions. Distal to the minor orifice, velocities measured only 70 and 80% of those downstream of the major orifice. In between, a region of relatively slow moving flow was present. The shape of the profiles remained essentially unchanged during acceleration and deceleration of flow. Thus, spatially resolved velocity profiles downstream of mechanical prostheses can be registered by an ultrasonic Doppler device. These findings may be useful for the detection of beginning malfunction both in the experimental and the clinical setting.

Hemodynamic evaluation by Doppler echocardiography of small (less than or equal to 21 mm) prostheses and bioprostheses in the aortic valve position

To assess resting hemodynamics of an unselected group of patients with prostheses or bioprostheses sized less than or equal to 21 mm implanted into the aortic valve position during a 7-year period, 46 of 50 eligible patients were examined by Doppler echocardiography. The valves were Carpentier-Edwards (CE) supraannular 21 mm (n = 8), Medtronic-Hall (MH) 20 mm (n = 8) and 21 mm (n = 21), and the rest (n = 9) were other valves with only 1 to 3 patients in each group. Gradients, valve areas and dimensionless obstruction indexes (ratio of subvalvular/valvular velocities and velocity time integrals) were compared. By analysis of variance, gradients did not differ significantly between the CE supraannular 21 mm, the MH 20 and 21 mm prostheses (peak/mean 25 +/- 8/14 +/- 5, 31 +/- 13/16 +/- 6 and 25 +/- 10/13 +/- 5 mm Hg; p = not significant). Only 2 patients had a mean gradient greater than 25 mm Hg. The valve area was slightly larger for the MH 21 mm group compared with the CE supraannular 21 mm group (1.34 +/- 0.15 vs 1.16 +/- 0.14 cm2, p less than 0.05). The dimensionless obstruction indexes did not differ (CE supraannular 21 mm 0.36 +/- 0.07/0.40 +/- 0.07 (velocities/velocity time integrals), MH 20 mm 0.40 +/- 0.12/0.47 +/- 0.12, MH 21 mm 0.38 +/- 0.05/0.44 +/- 0.06; p = not significant).(ABSTRACT TRUNCATED AT 250 WORDS)

The Hatle orifice area formula tested in normal bileaflet mechanical mitral prostheses

The Hatle formula was derived empirically in native mitral stenosis and may not be valid for normal prosthetic valves. Bileaflet mechanical prostheses open fully at low flows and have minimal interindividual variation in orifice area. In these valves effective area and measured manufacturer's area should be similar. We studied 60 patients aged 58 +/- 12 yr at a mean of 5 months after implantation with a CarboMedics prosthesis. There was a coexistent aortic prosthesis in 21. All diastolic measurements were averaged over 5 beats and stroke volume was calculated from the integral of the subaortic velocity trace and the cross-sectional area of the left ventricular outflow tract. For the whole group, area by the Hatle formula was 3.1 +/- 0.7 cm2 and measured area was 2.8 +/- 0.4 cm2. There was no significant correlation between these values (p = 0.329). Pressure half-time was more closely correlated with peak transmitral velocity (p = 0.012), RR interval (p = 0.015), diastolic time interval (p = 0.062) and stroke volume (p = 0.074). We conclude that the Hatle formula should not be applied to normal bileaflet mitral prostheses where pressure half-time reflects nonprosthetic factors more closely than orifice area.

Exercise evaluation of prosthetic heart valves by Doppler echocardiography: comparison with catheterization studies

Although valve replacement remains the cornerstone of treatment for critical heart valve dysfunction, problems including thromboembolism, infection, and primary failure of the prosthesis remain. Resting studies of valve hemodynamics are sometimes insufficient to reveal valve dysfunction. Early studies using cardiac catheterization focused on changes in prosthetic function seen with various types of exercise or drug-induced stress. These studies suffered from an inability to adequately stress catheterized patients and were cumbersome to the patient and the investigator. With the introduction of Doppler echocardiography, however, studies could be performed after significant exercise with low risk and increased ease. Using echocardiography, reports of exercise-induced changes in aortic and mitral valve hemodynamics have appeared. Over 600 patients have been studied using Doppler echocardiography. In the aortic position, all prostheses studied have a mild peak instantaneous gradient (18-26 mmHg) at rest, which increases with exercise (35-63 mmHg). No significant differences between the four models of mechanical prostheses studied are found. The gradients achieved with exercise do not appear to be related to the heart rate achieved or duration of exercise. Smaller prostheses are associated with larger gradients; however, the correlation was not strong. All mitral valve prostheses studied are also mildly stenotic at rest (range of mean gradients 2.3-7.1 mmHg) and become moderately stenotic with exercise (range 5.1-16.5). Although the lowest gradients are seen with St. Jude Medical and Medtronic Hall prostheses, their gradients are not significantly less than with other valves.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of prosthetic aortic valve design on the Doppler-catheter gradient correlation: an in vitro study of normal St. Jude, Medtronic-Hall, Starr-Edwards and Hancock valves

To evaluate the normal range of Doppler-derived velocities and gradients, their relation to direct flow measurements and the importance of prosthetic valve design on the relation between Doppler and catheter-derived gradients, five sizes of normal St. Jude bileaflet, Medtronic-Hall tilting disc, Starr-Edwards caged ball and Hancock bioprosthetic aortic valves were studied with use of a pulsatile flow model. A strong linear correlation between peak velocity and peak flow, and mean velocity and mean flow, was found in all four valve types (r = 0.96 to 0.99). In small St. Jude and Hancock valves, Doppler velocities and corresponding gradients increased dramatically with increasing flow, resulting in velocities and gradients as high as 4.7 m/s and 89 mm Hg, respectively. The ratio of velocity across the valve to velocity in front of the valve (velocity ratio) was independent of flow in all St. Jude, Medtronic-Hall, Starr-Edwards and Hancock valves when the two lowest flow rates were excluded for Hancock valves. Although Doppler peak and mean gradients correlated well with catheter peak and mean gradients in all four valve types, the actual agreement between the two techniques was acceptable only in Hancock and Medtronic-Hall valves. For St. Jude and Starr-Edwards valves, Doppler gradients significantly and consistently exceeded catheter gradients with differences as great as 44 mm Hg. Thus, Doppler velocities and gradients across normal prosthetic heart valves are highly flow dependent. However, the velocity ratio is independent of flow.(ABSTRACT TRUNCATED AT 250 WORDS)

Color Doppler regurgitant characteristics of normal mechanical mitral valve prostheses in vitro

BACKGROUND

To evaluate normal regurgitant characteristics of St. Jude (SJ) and Medtronic-Hall (MH) mitral valves, four sizes (25-31 mm) of each were studied in a pulsatile flow model.

METHODS AND RESULTS

Regurgitant flow was measured by flowmeter at left ventricular pressures of 80, 130, and 180 mm Hg. Peak regurgitant flow rates ranged from 6.2 to 12.7 cm3/sec in SJ valves and from 7.9 to 17.5 cm3/sec in MH valves. Regurgitant orifice areas calculated from the Doppler continuity equation ranged from 1.6 to 2.0 mm2 in SJ valves and from 2.2 to 2.9 mm2 in MH valves. Regurgitant volumes across the closed valve at a left ventricular pressure of 130 mm Hg were normalized to an ejection time of 280 msec and ranged from 1.5 to 1.9 cm3 in SJ valves and from 2.1 to 2.8 cm3 in MH valves. Jets were imaged by color Doppler in six rotational planes, and jet size and morphology were compared with those of regurgitant jets from circular orifices with sizes comparable to the calculated prosthetic valve regurgitant orifices (1.1-3.1 mm2). SJ valves showed two converging jets from the pivot points, one central jet, and a variable number of peripheral jets. The mean color jet area derived from the six image planes ranged from 1.6 to 5.3 cm2. Aliasing occurred only close to the valve (maximal distance 0.5-2.0 cm). MH valves showed a large central jet with a maximal length of aliased flow between 2.0 and 5.5 cm. Depending on valve size, driving pressure, and image plane, one or two small peripheral jets were found. These jets did not show aliasing in any case. The mean color jet area ranged from 5.1 to 11.0 cm2. Jets originating from circular orifices of comparable size showed jet areas from 5.5 to 13.9 cm2 and aliasing distances from 3.3 to 7.3 cm. At similar regurgitant orifice areas, driving pressures, and regurgitant flows, the measured color areas and aliasing distances were smallest in SJ valves, larger in MH valves, and largest in simple circular orifices.

CONCLUSIONS

Large, complex regurgitant jets can be found in normal closed SJ and MH valves by color Doppler, although regurgitant flow volume is minimal. Jet size and velocity distribution differs markedly between SJ valves, MH valves, and circular orifices, even with comparable driving pressure, regurgitant orifice area, and regurgitant volume. The characteristic patterns of normal regurgitation must be recognized to avoid incorrect diagnoses of pathological regurgitation in SJ and MH prosthetic valves. MH valves should not be removed solely on the basis of a central regurgitant jet with a long aliasing distance. Peripheral jets in MH valves and all jets in SJ valves should be considered normal as long as no or only minimal aliasing is present. In contrast, peripheral jets with significant aliasing may represent strong evidence of pathological regurgitation.

Hemodynamic evaluation of the CarboMedics prosthetic heart valve in the aortic position: comparison of noninvasive and invasive techniques

Seventy-three patients with a CarboMedics aortic bileaflet valve prosthesis were examined by Doppler ultrasonography, and 27 of them were also assessed by transseptal catheterization. The ultrasonic mean systolic gradient was 17.1 +/- 5.6 mm Hg for valve size 19 mm, falling gradually with increasing valve size to 6.8 +/- 2.5 mm Hg for size 27 mm. The catheter mean systolic gradient was consistently smaller than the ultrasonic gradient (4.3 +/- 4.8 mm Hg), but Tobit regression analysis showed a significant association between the two methods. In all patients both methods revealed negligible to small amounts of retrograde leakage, which is assumed to be a normal finding for this valve. The effective flow areas of the valves calculated from the ultrasonic data were similar to the in vitro calculated flow areas. The hemodynamic potential of this valve is therefore completely utilized in vivo. The effective orifice area corrected for body surface area increased with increasing valve size, which demonstrates a moderate valve-patient mismatch.

Phonocardiogram spectral analysis simulator of mitral valve prostheses

Spectral analysis of sounds produced in vitro by mitral valve prostheses placed in a specially designed flow simulator has been carried out using a short-time Fourier representation of the recorded signal. Time variations of power spectra are displayed as a three-dimensional plot. Sounds produced by three types of valves, namely ball and cage, tilting disk and porcine valves, were analysed. Each valve type produced a characteristic spectrogram, and, for a given valve, spectrograms were reproducible to within a margin of 5 dB. The simulator may be used to detect structural deficiencies and functional abnormalities of prosthetic heart valves. In addition to quantifying the noise level of mechanical valves, the system may be used for quality control purposes to identify faulty valves.

Pathologic and angiographic correlations of transesophageal echocardiography in prosthetic heart valve dysfunction

To determine the diagnostic accuracy of transesophageal echocardiography (TEE) in prosthetic valve dysfunction, the pathologic and/or angiographic data from 37 valves were compared with that obtained by transesophageal and transthoracic echocardiography. Of the 21 prostheses with severe regurgitation, TEE identified all 14 mitral, the five aortic, and one of the two tricuspid valves; on the other hand transthoracic echocardiography identified 2 of the 14 mitral, the five aortic, and one of the two tricuspid valves. Of the 10 prostheses with flail cusp(s), nine (90%) were correctly identified by TEE and four (40%) were correctly identified by transthoracic echocardiography. All five prostheses with paravalvular regurgitation were detected through the esophageal window and one detected through the precordial window. TEE was unable to document the two prosthetic aortic stenoses, whereas the transthoracic examination correctly quantified the gradient in one but underestimated it in the other case. Seven patients underwent valve replacement on the basis of the clinical and TEE information alone. In assessing cause, origin, and severity of prosthetic mitral regurgitation, TEE is the method of choice. In selected cases, TEE can avoid angiography and facilitate optimal timing of reoperation. In selected aortic and tricuspid dysfunction, TEE may provide additional morphologic, but limited hemodynamic information.

Value and limitations of transesophageal echocardiography in assessment of mitral valve prostheses

BACKGROUND

Transthoracic Doppler echocardiography examination has become an integral part of the investigations performed in patients with mitral valve prostheses. The limitations of the transthoracic approach are well documented. Transesophageal echocardiography provides a unique window for achieving a clear view of the mitral prosthesis.

METHODS AND RESULTS

This study shows the usefulness of transesophageal echocardiography in clinical practice for assessment of patients with a mitral valve prosthesis. This technique demonstrated an abnormality in 48% of patients who had normal results on transthoracic examination. The overall sensitivity of transesophageal echocardiography was 96%.

CONCLUSIONS

Transesophageal echocardiography constitutes an essential part of a comprehensive two-dimensional/Doppler echocardiographic examination in patients with suspected malfunction of mitral prostheses.

Validity of an early postoperative baseline Doppler recording after aortic valve replacement

In 131 patients undergoing aortic valve replacement (53 bioprostheses, 78 mechanical), the pressure decrease across the prosthesis was recorded with Doppler ultrasound at a baseline study early postoperatively (mean 11 +/- 5 days) and compared with a repeat measurement 3 to 5 months later. At baseline the hemodynamic state was markedly different, with increased heart rate (89 +/- 14 vs. 74 +/- 13 beats/min, p less than 0.001) and decreased left ventricular ejection time index (367 +/- 21 vs 390 +/- 22, p less than 0.001). A minor and clinically insignificant decrease in pressure decrease with time was found. The 95% confidence interval for the difference was 0.2 to 3.0 and 0.2 to 1.7 mm Hg for the peak and the mean pressure decrease, respectively. The change in pressure decrease was statistically significant for bioprostheses (mean 16 +/- 5 vs 14 +/- 4 mm Hg, p less than 0.01) and smaller (less than or equal to 23 mm) valves (mean 17 +/- 4 vs 15 +/- 4 mm Hg, p less than 0.01), whereas no significant changes were found for mechanical valves or valves of a larger size. The change in mean pressure decrease from baseline to the second examination was within +/- 5 mm Hg for 82% of patients. It is concluded that despite a different hemodynamic state in the early postoperative period, the pressure decrease across aortic valve prostheses obtained at this time can be used as a reference for later comparison.

Doppler echocardiographic study of porcine bioprosthetic heart valves in the aortic valve position in patients without evidence of cardiac dysfunction

To study the natural history of the hemodynamic performance of bioprosthetic heart valves, Doppler echocardiograms were recorded in a group of clinically stable patients at 2 and 5 years after replacement of native aortic valves with bioprosthetic valves. Eighteen patients completed a 2-year and 26 patients a 5-year follow-up examination. The effective orifice areas of identical models of bioprosthetic valves (Hancock II) were determined in vitro in a left-sided heart pulse duplicator system. In vivo Doppler-derived effective orifice areas were compared with the in vitro measurements for the same valve size. At both the 2- and 5-year follow-up examinations, the Doppler-derived effective orifice area was significantly less than the in vitro area (p less than 0.0001 at each interval). Ten of 16 valves evaluated serially decreased greater than 0.20 cm2 in the Doppler-derived effective orifice area between studies. The mean decrease in effective orifice area in valves evaluated serially was 0.25 +/- 0.29 cm2 (p less than 0.005). The peak transaortic gradient increased from 21 +/- 6 to 27 +/- 8 mm Hg (p less than 0.01). The mean transaortic gradient increased from 12 +/- 4 to 15 +/- 7 mm Hg (p less than 0.05). It is concluded that serial Doppler echocardiographic studies demonstrate a deterioration in the hemodynamic performance of bioprosthetic valves over time in patients with no symptoms or signs of valvular dysfunction and that Doppler echocardiography may be useful for identifying subclinical bioprosthetic valvular dysfunction.

Doppler echocardiographic assessment of prosthetic aortic valve function. Findings in normal valves

To determine the Doppler-derived aortic flow velocity profiles in relation to type of prosthetic valve and left ventricular function, 70 patients with normal functioning aortic prosthetic valves (group 1 = 44 patients with low-profile mechanical valves and group 2 = 26 patients with high-profile mechanical valves) were evaluated. Peak flow velocity and mean systolic gradient were inversely related to valve size (r = -0.72; r = -0.76) in group 1. On the other hand, aortic flow velocity profiles had significant correlations with left ventricular end-systolic dimension (r = 0.75; r = 0.76) and left ventricular fractional shortening (r = -0.69; r = -0.66) in group 2. Thus, aortic flow velocity profiles in the low-profile mechanical valve were affected by pressure gradient caused by the valve size, whereas the hydromechanical disadvantage of the high profile mechanical valve affected the left ventricular pump function and Doppler-derived flow velocity profiles.